Rotatable Cutting Tool With Continuous Arcuate Head Portion

ABSTRACT

A rotatable cutting tool for use in impinging earth strata wherein the rotatable cutting tool includes a cutting tool body and a hard tip affixed to the cutting tool body. The cutting tool body includes a forward end for receiving the hard tip and a rearward end, a head portion, a collar portion, and a shank portion. In one aspect, the head portion includes a continuous arcuate outer surface providing a slim profile.

BACKGROUND OF THE INVENTION

The invention pertains to a rotatable cutting tool that is useful forthe impingement of earth strata such as, for example, asphaltic roadwaymaterial, coal deposits, mineral formations and the like. Morespecifically, the present invention pertains to a rotatable cutting toolthat is useful for the impingement of earth strata wherein the cuttingtool body possesses an improved design so as to provide for improvedperformance characteristics for the entire rotatable cutting tool.

Rotatable cutting tools have been used to impinge earth strata such as,for example, asphaltic roadway material or ore bearing or coal bearingearth formations or the like. Generally speaking, these kinds ofrotatable cutting tools have an elongate cutting tool body, typicallymade from steel, and a hard tip (or insert) affixed to the cutting toolbody at the axial forward end thereof. The hard tip is typically madefrom a hard material such as, for example, cemented (cobalt) tungstencarbide. The rotatable cutting tool is rotatably retained or held in thebore of a tool holder or, in the alternative, in the bore of a sleevethat is in turn held in the bore of a holder.

The holder is affixed to a driven member such as, for example, a drivendrum of a road planing machine. In some designs, the driven member(e.g., drum) carries hundreds of holders wherein each holder carries arotatable cutting tool. Hence, the driven member may carry hundreds ofrotatable cutting tools. The driven member is driven (e.g., rotated) insuch a fashion so that the hard tip of each one of the rotatable cuttingtools impinges or impacts the earth strata (e.g., asphaltic roadwaymaterial) thereby fracturing and breaking up the material into debris.

As can be appreciated, during operation the entire rotatable cuttingtool is typically subjected to a variety of extreme cutting forces andstresses in an abrasive and erosive environment. It would be undesirablefor the cutting tool body to prematurely wear or fail (whether it bethrough catastrophic fracture or the like or through abrasive or erosivewear) prior to the hard cutting tip wearing to the point of its usefullife. In such a circumstance, the rotatable cutting tool would have tobe replaced prior to the normally scheduled time for replacement.Further, the premature failure of the rotatable cutting tool wouldnegatively impact the cutting or milling efficiency of the overallearthworking apparatus. It thus becomes apparent that it is importantthat the cutting tool body possess the requisite design and strength tomaintain its integrity during the intended useful life of the rotatablecutting tool.

SUMMARY OF THE INVENTION

The present invention provides a rotatable cutting tool for use inimpinging earth strata wherein the rotatable cutting tool includes ahead portion having an arcuate outer surface from an axial forward endto an axial rearward end thereof. The arcuate outer surface of the headportion of the rotatable cutting tool provides for a slimmer profilewhile maintaining sufficient strength to withstand the forces andstresses that the rotatable cutting tool is subjected to duringoperation.

An aspect of the present invention is to provide a rotatable cuttingtool for use in impinging earth strata wherein the rotatable cuttingtool includes a cutting tool body and a hard tip affixed to the cuttingtool body. The cutting tool body includes an axial forward end forreceiving the hard tip and an axial rearward end, a head portion axiallyrearward of the axial forward end, a collar portion axially rearward ofthe head portion, and a shank portion axially rearward of the collarportion and axially forward of the axial rearward end. The head portionincludes an axial forward generally circular cross-section having anaxial forward diameter and an axial rearward generally circularcross-section having an axial rearward diameter. The diameter of thehead portion decreases non-linearly from the axial rearward diameter tothe axial forward diameter.

Another aspect of the present invention is to provide a rotatablecutting tool for use in impinging earth strata wherein the rotatablecutting tool includes a cutting tool body and a hard tip affixed to thecutting tool body. The cutting tool body includes an axial forward endfor receiving the hard tip and an axial rearward end, a head portionaxially rearward of the axial forward end, a collar portion axiallyrearward of the head portion, and a shank portion axially rearward ofthe collar portion and axially forward of the axial rearward end. Thehead portion includes an axial forward periphery and an axial rearwardperiphery, wherein the head portion further includes a continuousarcuate outer surface extending from the axial forward periphery to theaxial rearward periphery.

A further aspect of the present invention is to provide a rotatablecutting tool body with a central longitudinal axis wherein the rotatablecutting tool body includes a head portion, a shank portion, and a collarportion mediate of and contiguous with the head portion and shankportion. The cutting tool body further includes an axial forward endadjacent to the head portion and an axial rearward end adjacent to theshank portion. The head portion includes an axial forward periphery andan axial rearward periphery, wherein the head portion further includes acontinuous arcuate outer surface extending from the axial forwardperiphery to the axial rearward periphery.

These and other aspects of the present invention will be more fullyunderstood following a review of this specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a side view of a rotatable cutting tool, inaccordance with an aspect of the invention.

FIG. 2 is a forward end view of the rotatable cutting tool shown in FIG.1 (with the hard insert removed), in accordance with an aspect of theinvention.

FIG. 3 is an enlarged side view of a portion of the rotatable cuttingtool shown in FIG. 1 (with the hard insert removed), in accordance withan aspect of the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a rotatable cutting tool, generally designated as 20,in accordance with an aspect of the invention. Rotatable cutting tool 20comprises an elongate cutting tool body, generally designated as 22. Thecutting tool body 22 is typically made of steel such as those gradesdisclosed, for example, in U.S. Pat. No. 4,886,710 to Greenfield, whichis hereby incorporated by reference.

Still referring to FIG. 1, the cutting tool body 22 has an axial forwardend 24 and an axial rearward end 26. A hard tip or insert 30 is affixed(such as by brazing or the like) in a socket 31 in the axial forward end24 of the cutting tool body 22. Hard insert 30 is typically made fromcemented carbide such as, for example, cemented (cobalt) tungstencarbide wherein U.S. Pat. No. 6,375,272 to Ojanen, which is herebyincorporated by reference, discloses examples of acceptable grades ofcemented (cobalt) tungsten carbide. The geometry of the hard insert 30can vary depending upon the specific application. U.S. Pat. No.6,375,272 to Ojanen discloses an exemplary geometry for the hard insert.It should be appreciated that as an alternative to the socket, the axialforward end of the cutting tool body may present a projection that isreceived within a socket in the bottom of the hard tip. This alternatestructure can be along the lines of that disclosed, for example, in U.S.Pat. No. 5,141,289 to Stiffler, which is hereby incorporated byreference.

The cutting tool body 22 is divided into three principal portions;namely, a head portion, a collar portion and a shank portion. Theseportions will now be described.

The most axial forward portion is a head portion (see bracket 32). Thehead portion 32 begins at the axial forward end 24 and extends alonglongitudinal axis X-X in the axial rearward direction for a distance A.In one aspect of the invention, distance A is in the range of about 2.0centimeters to about 16.0 centimeters.

The mediate portion is the collar portion (see bracket 38). Beginning atthe juncture with the head portion 32 and extending along thelongitudinal axis X-X in the axial rearward direction for a distance B,the collar portion 38 comprises a tapered neck section 40 followed by acylindrical collar section 42.

The most axial rearward portion is the shank portion (see bracket 44).Beginning at the juncture with the collar portion 38 and extending alongthe longitudinal axis X-X in the axial rearward direction for a distanceC, the shank portion 44 comprises a beveled section 46 followed by aforward cylindrical tail section 48, followed by a retainer groove 50,followed by a rearward cylindrical tail section 52 and terminating in abeveled section 54. As is known by those skilled in the art, the shankportion 44 is the portion of the cutting tool body 22 that carries theretainer (not illustrated). The retainer rotatably retains the rotatablecutting tool in the bore of a tool holder (not illustrated) or the boreof the sleeve carried by a holder. While the retainer can take on anyone of many geometries, a retainer suitable for use with this cuttingtool body is shown and described, for example, in U.S. Pat. No.4,850,649 to Beach et al., which is hereby incorporated by reference.

Referring to FIGS. 1 and 2, the head portion 32 includes an axialforward periphery 56 adjacent to the axial forward end 24 thereof. Theaxial forward periphery 56 defines an axial forward generally circularcross section of the head portion 32 having an axial forward diameter(labeled as FD). The axial forward diameter FD is in the range of about0.50 centimeters to about 5.50 centimeters. Similarly, the head portion32 includes an axial rearward periphery 58 adjacent to the collarportion 38. The axial rearward periphery 58 defines an axial rearwardgenerally circular cross section of the head portion 32 having an axialrearward diameter (labeled as RD). The axial rearward diameter RD is inthe range of about 0.60 centimeters to about 7.70 centimeters.

As shown in FIGS. 1 and 3, the head portion 32 includes a continuousarcuate outer surface 60 extending from the axial forward periphery 56to the axial rearward periphery 58. The outer surface 60 thus has aradius of curvature, labeled as arrow RC, to provide the arcuate outersurface 60 extending from the axial forward periphery 56 to the axialrearward periphery 58. The radius of curvature RC is in the range ofabout 12.0 centimeters to about 130.0 centimeters.

Still referring to FIGS. 1 and 3, the diameter of the head portion 32decreases non-linearly from the axial rearward periphery 58 to the axialforward periphery 56. In other words, the head portion 32 includes amaximum diameter at the axial rearward diameter RD thereof and thediameter of the head portion 32 decreases non-linearly to a minimumdiameter at the axial forward diameter FD of the head portion. The term“non-linearly” as used herein generally refers to the changing diameterof the head portion being such that the outer surface 60 of the headportion 32 remains continuously arcuate from the axial rearwardperiphery 58 to the axial forward periphery 56 and that the outersurface is not straight or flat along any section thereof from the axialrearward periphery 58 to the axial forward periphery 56.

EXAMPLE

An exemplary set of dimensions for head portion 32 (wherein the headportion 32 is formed, for example, of 4140 steel that has been heattreated to have a Rockwell C hardness in the range of about 45-50) is asfollows:

TABLE 1 Distance L Diameter d (centimeters) (centimeters) 0.6351.2127738 1.27 2.520235904 1.905 1.8660872 2.54 2.074799 3.175 2.24977963.81 2.4019256 4.445 2.53746 5.08 2.6602944 5.715 2.7729942 6.352.877439

Where:

-   L=Distance from axial forward end 24 to point of calculated diameter    d (see FIG. 3)-   d=Diameter of head portion 32 at distance L (see FIG. 3)-   The dimensions set forth in Table 1 were calculated using the    following equations:

Maximum Nominal Tensile Stress

$\sigma_{a}^{\prime} = {\frac{1.273}{d^{2}}\left( {\frac{8{LF}_{y}}{d} - F_{x}} \right)}$

Maximum Nominal Compressive Stress

$\sigma_{b}^{\prime} = {\frac{1.273}{d^{2}}\left( {\frac{8{LF}_{y}}{d} + F_{x}} \right)}$

Maximum Nominal Shear Stress

τ_(a)′=0.5σ_(a)′

τ_(b)′=0.5σ_(b)′

-   σ_(a)′=Maximum allowable tensile stress-   σ_(b)′=Maximum allowable compressive stress-   τ_(a)′ and τ_(b)′=Maximum allowable tensile stress-   F_(y)=Force component in the Y direction-   F_(x)=Force component in the X direction    In this example, for the heat treated 4140 steel    σ_(a)′=σ_(b)′=851.734 MPa, and the desired forces that the head    portion must withstand is F_(y)=24643.15 N, and F_(x)=31546.79 N.    Using these values and selecting distances L at every 0.635 cm along    the length of the head portion, the diameter d at each distance L    was found, as illustrated in Table 1. This results in the head    portion 32 forming a profile that gives the continuous arcuate outer    surface 60 having radius RC. In this example, the value of radius RC    of the arcuate outer surface 60 of the head portion 32 is RC=22.0    cm.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. A rotatable cutting tool for use in impinging earth strata, therotatable cutting tool comprising: a cutting tool body; a hard tipaffixed to the cutting tool body; the cutting tool body having an axialforward end for receiving the hard tip and an axial rearward end, a headportion axially rearward of the axial forward end, a collar portionaxially rearward of the head portion, and a shank portion axiallyrearward of the collar portion and axially forward of the axial rearwardend; and wherein the head portion includes an axial forward generallycircular cross section having an axial forward diameter and an axialrearward generally circular cross section having an axial rearwarddiameter, wherein the diameter of the head portion decreasesnon-linearly from the axial rearward diameter to the axial forwarddiameter.
 2. The rotatable cutting tool of claim 1, wherein the axialforward diameter is in the range of about 0.50 centimeters to about 5.50centimeters.
 3. The rotatable cutting tool of claim 1, wherein the axialrearward diameter is in the range of about 0.60 centimeters to about7.70 centimeters.
 4. The rotatable cutting tool of claim 1, wherein thehead portion includes a continuous arcuate outer surface extending fromthe axial forward diameter to the axial rearward diameter.
 5. Therotatable cutting tool of claim 4, wherein the continuous arcuate outersurface has a radius of curvature in the range of about 12.0 centimetersto about 130.0 centimeters.
 6. The rotatable cutting tool of claim 1,wherein the head portion includes an axial forward periphery and anaxial rearward periphery, wherein the head portion further includes acontinuous arcuate outer surface extending from the axial forwardperiphery to the axial rearward periphery.
 7. The rotatable cutting toolof claim 6, wherein the continuous arcuate outer surface has a radius ofcurvature in the range of about 12.0 centimeters to about 130.0centimeters.
 8. The rotatable cutting tool of claim 1, wherein the headportion has an axial length in the range of about 2.0 centimeters toabout 16.0 centimeters.
 9. A rotatable cutting tool for use in impingingearth strata, the rotatable cutting tool comprising: a cutting toolbody; a hard tip affixed to the cutting tool body; the cutting tool bodyhaving an axial forward end for receiving the hard tip and an axialrearward end, a head portion axially rearward of the axial forward end,a neck portion axially rearward of the head portion, a collar portionaxially rearward of the mediate portion and a shank portion axiallyrearward of the collar portion and axially forward of the axial rearwardend; and wherein the head portion includes an axial forward peripheryand an axial rearward periphery, wherein the head portion furtherincludes a continuous arcuate outer surface extending from the axialforward periphery to the axial rearward periphery.
 10. The rotatablecutting tool of claim 9, wherein the continuous arcuate outer surfacehas a radius of curvature in the range of about 12.0 centimeters toabout 130.0 centimeters.
 11. The rotatable cutting tool of claim 9,wherein the head portion has an axial length in the range of about 2.0centimeters to about 16.0 centimeters.
 12. The rotatable cutting tool ofclaim 9, wherein a diameter of the head portion decreases non-linearlyfrom the axial rearward periphery to the axial forward periphery.
 13. Arotatable cutting tool body with a central longitudinal axis, therotatable cutting tool body comprising: a head portion, a shank portion,and a collar portion mediate of and contiguous with the head portion andthe shank portion; an axial forward end adjacent to the head portion andan axial rearward end adjacent to the shank portion; wherein the headportion includes an axial forward periphery and an axial rearwardperiphery, wherein the head portion further includes a continuousarcuate outer surface extending from the axial forward periphery to theaxial rearward periphery.
 14. The rotatable cutting tool body of claim13, wherein the continuous arcuate outer surface has a radius ofcurvature in the range of about 12.0 centimeters to about 130.0centimeters.
 15. The rotatable cutting tool body of claim 13, whereinthe head portion has an axial length in the range of about 2.0centimeters to about 16.0 centimeters.
 16. The rotatable cutting toolbody of claim 13, wherein a diameter of the head portion decreasesnon-linearly from the axial rearward periphery to the axial forwardperiphery.
 17. The rotatable cutting tool body of claim 13, wherein thehead portion includes an axial forward generally circular cross sectionhaving an axial forward diameter and an axial rearward generallycircular cross section having an axial rearward diameter, wherein thediameter of the head portion decreases non-linearly from the axialrearward diameter to the axial forward diameter.
 18. The rotatablecutting tool body of claim 17, wherein the axial forward diameter is inthe range of about 0.50 centimeters to about 5.50 centimeters.
 19. Therotatable cutting tool body of claim 17, wherein the axial rearwarddiameter is in the range of about 0.60 centimeters to about 7.70centimeters.
 20. A rotatable cutting tool body with a centrallongitudinal axis, the rotatable cutting tool body comprising: a headportion, a shank portion, and a collar portion mediate of and contiguouswith the head portion and the shank portion; an axial forward endadjacent to the head portion and an axial rearward end adjacent to theshank portion; wherein the head portion includes an axial forwardgenerally circular cross section having an axial forward diameter and anaxial rearward generally circular cross section having an axial rearwarddiameter, wherein the diameter of the head portion decreasesnon-linearly from the axial rearward diameter to the axial forwarddiameter.
 21. The rotatable cutting tool body of claim 20, wherein theaxial forward diameter is in the range of about 0.50 centimeters toabout 5.50 centimeters.
 22. The rotatable cutting tool body of claim 20,wherein the axial rearward diameter is in the range of about 0.60centimeters to about 7.70 centimeters.